1. Field of the Invention
The present invention relates generally to providing routing functions for navigation systems. In particular, the present invention is directed to more efficient specification of navigation routes.
2. Description of the Related Art
Navigation systems for drivers and pedestrians are becoming increasingly popular in the market. Until recently, most navigation systems were self-contained devices: routes were calculated and points of interest were searched for by means of calculations taking place entirely on the device. A few navigation systems, with less memory and slower processors, were primarily server-based: navigation requests were sent to a server, a route was computed and transmitted to the client device, and then the client device merely monitored progress along the route.
Now, with the advent of cheaper, faster processors in client devices and connections between clients and servers that offer greater bandwidth and more constant connectivity, a new model of navigation is becoming available. In this model, which can be called “connected navigation”, the client device can do most of the work of the navigation system, but in addition, certain other functions can be delegated to a server. This model is most advantageous when the functions delegated to the server are those that require either more computational power than is available on the client device or volumes of data too great to transmit to the client efficiently.
One example of such a function is routing that takes current and predicted traffic into account. Some modern automatic traffic information feeds provide current traffic information for all major roads in a metropolitan area, as well as predicted traffic information for every major road for every 15-minute interval of time for the next week. This is a very large amount of information, of which only a very small fraction is actually used to compute any given route. It is therefore very inefficient to transmit all the data to every client device in the area.